FUNCTIONS OF SPINAL CORD. ENCEPHALON. 141 



Functions of the spinal cord. We have already seen that 

 the anterior fascicles of the spinal cord are insensitive, and 

 that they give motor power to the anterior roots of the nerve, 

 while the posterior portions are sensitive, like the nerves 

 which emerge from them. These properties of the medul- 

 lary fascicles were for a long period disputed, but they have 

 been clearly demonstrated by M. Longet's experiments. 

 The spinal cord imparts to the nerves of the trunk and limbs 

 the power of voluntary and respiratory motion. It is also 

 the source of nervous energy in the action of the heart, and 

 in the circulation of the blood, in the phenomena of nutrition 

 and of secretion; lastly, it seems to have only an indirect in- 

 fluence on the production and maintenance of animal heat. 

 When there is any lesion of one of the lateral halves of the 

 cord, it is on the corresponding side of the body that motion 

 and sensation are disturbed or destroyed. The action 

 therefore of the spinal cord is direct on the organs to which 

 it sends nerves, and not crossed like that of the encephalon. 



Functions of the encephalon. Medulla oblongata. The me- 

 dulla is the central source and regulator of the respiratory 

 movements. It is in a limited portion of this enlargement 

 of the cord, near the origin of the eighth pair of nerves, that, 

 as Flourens has demonstrated, the organ which he calls the 

 prime mover, or vital node, of the respiratory mechanism has 

 its seat. This organ, according to M. Longet, does not 

 comprise all the substance of the bulb, but is only a fascicle, 

 composed of gray substance between the pyramidal and 

 restiform bodies. The medulla transmits impressions from 

 the cord to the brain, and the impulse of the will from the 

 brain to the cord; its anterior and posterior portions are 

 prolongations of the corresponding medullary fascicles, and 

 we may conclude therefore that they share their functions as 

 they do their substance; and that the medulla by its ante- 

 rior portion controls movement, and by its posterior portion 

 sensation. In point of fact, all the nerves which spring from 

 the anterior portion are sensitive, and from the posterior 

 motor. The anterior fascicles of the medulla cross their 

 fibres, and from this results a cross action on the motor 

 nerves, which originate from these fascicles; the posterior 



